In essence you can have what ever you want, but at a cost, and this is the problem BG do jobs at a fixed price in their standard method. The Hive system can work either way around the motorised valves can tell the wall thermostat when to switch boiler on, or the wall thermostat can tell motorised valves to open and they tell the boiler when to fire. They are completely different methods, and to swap will cost.
So the standard motorised valve has micro switches inside it and is either on or off, the thermostatic radiator valve (TRV) can be made into a motorised valve by adding the Hive head to it, which uses a heat on demand system to tell the wall thermostat when to turn on boiler, and the converted TRV has the advantage of slowly opening and closing so each room is gradually controlled so reducing the hysteresis, and you can have a heat on each radiator so each room is independent.
The Hive TRV head was only released last year, it does not seem to get very good reviews, but all I can say it what the advert says it can do, I also made mistakes with the central heating, I installed Nest and Energenie TRV heads and I have found the claimed linking in practice did not work, the heads do turn each TRV into a motorised valve and they do work well at controlling the rooms, but the linking so the auto follow Nest has not worked, so the cheap eQ-3 in real terms for me do just as good of a job.
And the cost is the problem,
screwfix around £54 each, else where you can find cheaper seen on ebay for £40, eQ-3
screwfix £22, else where seen them for £10 and I got bluetooth versions for £15. But this house 13 TRV's so looking at £600 for the heads if all Hive, and £130 if all eQ-3 as said I have Nest not Hive so I have 4 x Energenie and 5 x eQ-3 bluetooth, and not perfect but good enough, so you have to decide how much your willing to pay?
It does depend on the house, in last 10 years I have lived in three houses with central heating, my old house was open plan, and down stairs was controlled by a single thermostat, and upstairs the TRV's stopped bedrooms over heating, nothing complex, it did not need it, the Myson fan assisted radiator would heat down stairs fast, and there was also a 4.5 kW gas fire, so no need to pre-heat house, I could get it up to temp in 15 minutes.
Mothers house has bay windows, and these caused a problem, morning sun plus radiator could easy get living room to 32°C, adjusting the standard TRV improved it down to 28°C and with the electronic programmable TRV heads which work faster got it down to around 23°C when set temperature was 20°C when the sun came out. Without morning sun it was spot on. We also had the energenie TRV's in the bedrooms so 4 in all and they worked well in other rooms keeping them spot on, with gas boiler modulating and thermostat and TRV in hall.
We brought the TRV heads with us to this house, again large area of glass in living room in this case patio doors, and again morning sun can be a problem, the TRV heads do not work as well as have an oil boiler which does not modulate, however they still do work well keeping rooms to the temperature set on the schedule.
However the point is life style and house design mean what works well in one house or for one family may not work for another, this house takes longer to heat up, and the geofencing and occupancy detection is really handy warming up the house before we get home, which as said was not required with the old house.
So you have to decide what your willing to pay for. I find we tend to leave doors open, so although the dinning room is not heated until 4 pm, it gets heat from the hall, and heat raises so if we leave bedroom doors open even with schedule set not to heat in the day, they will still get warm, so although theory is rooms only heated when required, in practice the whole house is still heated, may be not as much, but no room is ever what one would say is cold, maybe 14°C but that is not really cold, again switch a bank of radiators on/off in theory with modulating boilers is not as good as gradually controlling individual rooms, but as to if there are savings worth worrying about allowing the boiler to modulate as it is designed to do, rather than switching on/off, I really don't know.
The theory is the modulating boiler turns slowly down as the TRV's close so when it finally stops it is already cool so less heat lost out of flue, not convinced it makes that much difference. And it does not matter for me as oil fired so does not modulate.
So Drayton Wiser, EvoHome, and Tado are really good systems controlling each room independently using where the boiler allows opentherm gradual control, Nest also has opentherm but does not have such a good way to integrate with the TRV heads, Hive does not have opentherm but does have TRV heads which are claimed to work with it. No one is likely to have lived in a house paying bill with all 5 systems, so no one can really say which is best, or how much one costs compared with another, however unless the TRV heads control the rooms non will work A1, but as to if it is worth the cost to buy all those expensive TRV heads, I don't know, I as said use eQ-3 there is also the Terrier i30 which is nearly the same.
